Improving Power Output of Battery and Mode Switching Frequency Based on Real-Time Average Power Method for Multi-Mode Hybrid Energy Storage System in Electric Vehicles

This paper presents a power-split strategy based on a average power method is developed for improving power output of battery and mode switching frequency of a multi-mode hybrid energy storage system (HESS) in electric vehicles. To achieve mode switching and power distribution for the multi-mode HESS, a rule-based strategy is designed based on the high-frequency power demand. Furthermore, a simple real-time average power method is adopted to process the high-frequency power demand. Then, average power is used as a variable logic threshold value for the power-split strategy. Since the power-split controller responds to the smooth average power rather than the high-frequency power demand, the high-frequency mode switching of the multi-mode HESS can be avoided. The ultra-capacitor works as an enhanced low-pass power filter and the battery can supply smooth and steady output power to the motor inverter. The simulation results can be evaluated by using Matlab/Simulink Software.

 Keywords: Electric vehicles, battery, ultra-capacitor, hybrid energy storage system, power-split strategy, mode switching.